蒸汽相变促进可溶PM2.5凝结增长的数值分析

为利用蒸汽相变原理促进氨法脱硫系统排放细颗粒物(PM2.5)的脱除,建立多分散颗粒的凝结增长动力学模型,利用数值模拟方法研究了可溶硫酸铵颗粒的凝结增长规律,并将典型粒径可溶与不可溶颗粒的凝结增长过程进行对比分析.结果表明:不同粒径硫酸铵颗粒的增长速率相近,等温系统的凝结增长效果优于绝热系统;对于同一初始粒径分布下的可溶和不可溶颗粒,微米尺度可溶颗粒的增长速率始终大于不可溶颗粒,亚微米尺度可溶颗粒的增长速率先大于而后小于不可溶颗粒,使得二者的增长曲线存在一个交叉点;蒸汽饱和度增大能显著促进硫酸铵颗粒的增长;等温系统中温度对硫酸铵颗粒的增长影响显著,绝热系统中温度的影响较弱.

Numerical analysis on growth of soluble PM2.5 by vapor heterogeneous condensation

In order to remove the fine particles (PM2.5) from ammonia desulfurization system by vapor heterogeneous condensation, the dynamic model for condensation growth of polydispersed particles was established. The condensation growth of soluble ammonium sulfate particles was numerically investigated and the growth processes of typical size soluble particles were analyzed and compared to those of insoluble particles. The ammonium sulfate particles of different sizes appear to grow at a similar rate and that more effective particle growth can be achieved in the isothermal system than in the adiabatic system. For the soluble and insoluble particles with the same initial size distribution, the growth rate of the micron soluble particles is higher than that of insoluble particles; whereas the growth rate of the submicron soluble particles is higher at first and then lower than that of the insoluble particles, thus the growth curves for the two kinds of particles have a cross point. The growth of ammonium sulfate particles can be significantly promoted by increasing vapor saturation. Strong influence of gas temperature on growth of ammonium sulfate particles in the isothermal system is observed whereas the effect of gas temperature on particle growth in the adiabatic system is very weak.